<p>There are few studies have mentioned the influence of trunk muscles relates to a bicycle pedaling. In our previous research, we therefore intended to construct a measurement system for estimate the trunk muscle force using inverse dynamics calculations in bicycle pedaling. The system consists of measurement devices, (1) reacting force of the bicycle (pedal force, saddle force, handle force), (2) Pedaling action (pedaling posture, crank angle) and (3) Electromyogram (EMG) of right leg. In this study, these measured value obtained from the system were try to use in the inverse dynamics problem of bicycle pedaling. As a result, current model of inverse dynamics calculation is not well matched to the actual muscle force, and the improvement of the analysis model is required.</p>